[R] macosx 10.8 install of rgl

[Greg Minshall]

by the, just in case anyone is wondering, on macosx 10.8 with Fink
0.34.4 and r-base215 (et al.), the following caused the R package rgl to
build, install, and (seemingly) work:
----
install.packages("rgl", configure.args='--with-gl-libs=/usr/X11/lib \
--disable-cocoa')
----

(without --with-gl-libs, -lGLU is not found, or -lX11 is not found;
without --disable-cocoa, osx/osxgui.o is not found [it appears that in
this case rgl is somewhat schizophrenic w.r.t. installing Mac-native
Cocoa support, which i didn't anyway want.)

cheers, Greg Minshall